1. Field of the Invention
This invention relates to a high-solids film-forming composition of a low molecular weight polyester with controlled hydroxyl functionality and an epoxy resin or ester of the resin and a monocarboxylic acid where the polyester and epoxy are crosslinked, during cure, with an aminoplast resin.
2. Description of the Prior Art
Conventional polyester-based coating compositions are well known in the finishes art, often comprising one or more hydroxyl-functional components which co-react with a suitable curing agent to form a polymeric paint film. For example, U.S. Pat. No. 3,994,851 issued Nov. 30, 1976 to Chang shows a specific polyester polyol which is cured with an amine-aldehyde condensation product.
A study of the related finishes art would make it evident, however, that in the field of polyester coatings, it is often necessary to sacrifice one desirable property to enhance another. For example, it is often difficult to obtain a coating composition that not only is applicable at high solids levels but also is tough, flexible, and durable. Also, coating compositions that are curable at lower temperatures often are insufficiently hard for industrial uses.
Therefore, with the current emphasis on reduction of solvent emissions, there is a continued need for coatings that not only can be applied at low solvent levels but also can be cured at commercially acceptable temperatures to produce a durable, flexible but hard, weather and stain resistant film.